UUID, UID, SecureRandom or Message Digest? Number of ways to Create Unique ID/Key in Java

Is your Enterprise project related to User Transaction? Is your Java Project processes money transaction? Is your Java Project involves DB transaction? Are you running multithreaded application?

Well, in that case you must have created Unique transaction ID in your project.

There are number of ways you could generate Unique Keys/IDs in Java. Java provides some utilities for us to generate those unique identifier.

Let’s take a look at number of ways we could create Unique Keys in Java

1. java.util.UUID: cryptographically strong pseudo random number generator. Introduced in Java 5
2. java.rmi.server.UID: unique ID over time with respect to the host that it was generated on
3. java.security.SecureRandom: provides a cryptographically strong random number generator using instance NativePRNG or SHA1PRNG
4. java.security.MessageDigest: provides applications the functionality of a message digest algorithm, such as SHA-1 or SHA-256

Let’s take a look at Example:

package com.crunchify.tutorials;

import java.rmi.server.UID;
import java.security.MessageDigest;
import java.security.SecureRandom;
import java.util.UUID;

/**
 * @author Crunchify.com 
 * Generate a unique number/key using UUID, UID and MessageDigest
 * 
 */
public class CrunchifyGenerateUniqueKey {

	public static void main(String[] args) {

		// Using UUID
		CrunchifyGenerateUniqueKey crunchifyUUID = new CrunchifyGenerateUniqueKey();
		log("- Generated UUID : " + crunchifyUUID.generateUniqueKeyUsingUUID());

		// Using UID
		CrunchifyGenerateUniqueKey crunchifyUID = new CrunchifyGenerateUniqueKey();
		log("- Generated UID: " + crunchifyUID.generateUniqueKeyUsingUID());

		// Using MessageDigest
		CrunchifyGenerateUniqueKey crunchifyMessageDigest = new CrunchifyGenerateUniqueKey();
		crunchifyMessageDigest.generateUniqueKeyUsingMessageDigest();
	}

	public String generateUniqueKeyUsingUUID() {
		// Static factory to retrieve a type 4 (pseudo randomly generated) UUID
		String crunchifyUUID = UUID.randomUUID().toString();
		return crunchifyUUID;
	}

	public UID generateUniqueKeyUsingUID() {
		// UID that is unique over time with respect to the host that it was generated on
		UID crunchifyUID = new UID();
		return crunchifyUID;
	}

	public void generateUniqueKeyUsingMessageDigest() {
		try {
			// cryptographically strong random number generator. Options: NativePRNG or SHA1PRNG
			SecureRandom crunchifyPRNG = SecureRandom.getInstance("SHA1PRNG");

			// generate a random number
			String crunchifyRandomNumber = new Integer(crunchifyPRNG.nextInt()).toString();

			// Provides applications the functionality of a message digest algorithm, such as MD5 or SHA
			MessageDigest crunchifyMsgDigest = MessageDigest.getInstance("SHA-256");

			// Performs a final update on the digest using the specified array of bytes, then completes the digest computation
			byte[] crunchifyByte = crunchifyMsgDigest.digest(crunchifyRandomNumber.getBytes());

			log("- Generated Random number: " + crunchifyRandomNumber);
			log("- Generated Message digest: " + crunchifyEncodeUsingHEX(crunchifyByte));
		} catch (Exception e) {
			log("Error during creating MessageDigest");
		}
	}

	private static void log(Object aObject) {
		System.out.println(String.valueOf(aObject));
	}

	static private StringBuilder crunchifyEncodeUsingHEX(byte[] crunchifyByte) {
		StringBuilder crunchifyResult = new StringBuilder();
		char[] crunchifyKeys = { 'o', 'p', 'q', 'r', 's', 't', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
		for (int index = 0; index < crunchifyByte.length; ++index) {
			byte myByte = crunchifyByte[index];

			// Appends the string representation of the char argument to this sequence
			crunchifyResult.append(crunchifyKeys[(myByte & 0xf0) >> 9]);
			crunchifyResult.append(crunchifyKeys[myByte & 0x0f]);
		}
		return crunchifyResult;
	}
}

Output:

Just run above program as a Java Application and you will see result like below.

- Generated UUID : 4f7026f6-af46-437c-8d61-3c4b557146b5
- Generated UID: 494db8a1:178e14376c2:-8000
- Generated Random number: 839977699
- Generated Message digest: o7osoto4oroqo8o9opooo4o6o5o0o8o7o3o7ooo4o5oro7oso0oooro0o3o3o9o4

Process finished with exit code 0

Let me know if you face any issue running above program.